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Hydrothermal-assisted exfoliation of Y/Tb/Eu ternary layered rare-earth hydroxides into tens of micron-sized unilamellar nanosheets for highly oriented and color-tunable nano-phosphor films.

Zhu Q, Xu Z, Li JG, Li X, Qi Y, Sun X - Nanoscale Res Lett (2015)

Bottom Line: The intercalation of oleate anions led to extremely expanded interlayer distances (up to approximately 5.2 nm) of the LRH crystals and accordingly disordered stacking of the ab planes along the c-axis and also weakened interlayer interactions, without significantly damaging the ab plane.Highly [111]-oriented and approximately 100-nm thick oxide films of (Y0.96Tb x Eu0.04-x ) 2O3 (0 ≤ x ≤ 0.04) have been obtained through spin-coating of the exfoliated colloidal nanosheets on quartz substrate, followed by annealing at 800°C.Upon UV excitation at 266 nm, the oxide transparent films exhibit bright luminescence, with the color-tunable emission from red to orange, yellow, and then green by increasing the Tb(3+) content from x = 0 to 0.04.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, No. 3-11, Wenhua Road, Shenyang, Liaoning 110819 China.

ABSTRACT
Efficient exfoliation of well-crystallized (Y0.96Tb x Eu0.04-x )2(OH)5NO3 · nH2O (0 ≤ x ≤ 0.04) layered rare-earth hydroxide (LRH) crystals into tens of micron-sized unilamellar nanosheets has been successfully achieved by inserting water insoluble oleate anions (C17H33COO(-)) into the interlayer of the LRH via hydrothermal anion exchange at 120°C, followed by delaminating in toluene. The intercalation of oleate anions led to extremely expanded interlayer distances (up to approximately 5.2 nm) of the LRH crystals and accordingly disordered stacking of the ab planes along the c-axis and also weakened interlayer interactions, without significantly damaging the ab plane. As a consequence, the thickness of the LRH crystals increased from approximately 1 to 10 μm, exhibiting a behavior similar to that observed from the smectite clay in water. Highly [111]-oriented and approximately 100-nm thick oxide films of (Y0.96Tb x Eu0.04-x ) 2O3 (0 ≤ x ≤ 0.04) have been obtained through spin-coating of the exfoliated colloidal nanosheets on quartz substrate, followed by annealing at 800°C. Upon UV excitation at 266 nm, the oxide transparent films exhibit bright luminescence, with the color-tunable emission from red to orange, yellow, and then green by increasing the Tb(3+) content from x = 0 to 0.04.

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FE-SEM, TEM, AFM images and height profile of the exfoliated nanosheets. (a) FE-SEM and (b) TEM micrographs showing morphologies of the nanosheets exfoliated from LRH-oleate (x = 0.035). The AFM images (c,d) and the height profile (e) along the red line marked in (c), respectively. The inset in (a) shows the appearance of a colloidal suspension of the nanosheets in toluene, with a clearly observable Tyndall effect under laser beam irradiation. The inset in (b) is the SAED pattern of an individual unilamellar nanosheet.
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Fig4: FE-SEM, TEM, AFM images and height profile of the exfoliated nanosheets. (a) FE-SEM and (b) TEM micrographs showing morphologies of the nanosheets exfoliated from LRH-oleate (x = 0.035). The AFM images (c,d) and the height profile (e) along the red line marked in (c), respectively. The inset in (a) shows the appearance of a colloidal suspension of the nanosheets in toluene, with a clearly observable Tyndall effect under laser beam irradiation. The inset in (b) is the SAED pattern of an individual unilamellar nanosheet.

Mentions: Dispersing the LRH-oleate in 50 mL of toluene yielded a transparent colloidal suspension via constant and slow magnetic stirring for 12 h. The clearly observable Tyndall effect under laser beam irradiation (inset in Figure 4a) indicates the delamination of LRH-oleate. FE-SEM observation found that most of the exfoliated nanosheets have lateral sizes of ≥20 μm (Figure 4a). The uniform contrast under TEM (Figure 4b) of the individual nanosheets implies that the nanosheet is rather thin. Selected area electron diffraction (SAED) yielded well-arranged spot-like patterns, suggesting that the nanosheet under observation is well crystallized and is of single crystalline (inset in Figure 4b). The cell parameters calculated from the SAED pattern are a ~ 1.27 and b ~ 0.72 nm, in good agreement with those of the bulk LRH [21]. The nanosheet was estimated to be approximately 1.55 nm thick from the AFM height profile (Figure 4e), indicating that the nanosheet is primarily of unilamellar. At the same time, AFM observation indicated that the nanosheets are very flat and smooth (Figures 4c,d). Possibly due to surface chemical adsorption of oleate and toluene molecules, the unilamellar nanosheets are a little thicker than the crystallographic thickness of 0.93 nm [24]. Compared with those reported previously [22,23], the unilamellar nanosheets obtained in this work showed a significantly larger lateral size and a more unabridged shape, which is advantageous for the construction of highly oriented functional films.Figure 4


Hydrothermal-assisted exfoliation of Y/Tb/Eu ternary layered rare-earth hydroxides into tens of micron-sized unilamellar nanosheets for highly oriented and color-tunable nano-phosphor films.

Zhu Q, Xu Z, Li JG, Li X, Qi Y, Sun X - Nanoscale Res Lett (2015)

FE-SEM, TEM, AFM images and height profile of the exfoliated nanosheets. (a) FE-SEM and (b) TEM micrographs showing morphologies of the nanosheets exfoliated from LRH-oleate (x = 0.035). The AFM images (c,d) and the height profile (e) along the red line marked in (c), respectively. The inset in (a) shows the appearance of a colloidal suspension of the nanosheets in toluene, with a clearly observable Tyndall effect under laser beam irradiation. The inset in (b) is the SAED pattern of an individual unilamellar nanosheet.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385236&req=5

Fig4: FE-SEM, TEM, AFM images and height profile of the exfoliated nanosheets. (a) FE-SEM and (b) TEM micrographs showing morphologies of the nanosheets exfoliated from LRH-oleate (x = 0.035). The AFM images (c,d) and the height profile (e) along the red line marked in (c), respectively. The inset in (a) shows the appearance of a colloidal suspension of the nanosheets in toluene, with a clearly observable Tyndall effect under laser beam irradiation. The inset in (b) is the SAED pattern of an individual unilamellar nanosheet.
Mentions: Dispersing the LRH-oleate in 50 mL of toluene yielded a transparent colloidal suspension via constant and slow magnetic stirring for 12 h. The clearly observable Tyndall effect under laser beam irradiation (inset in Figure 4a) indicates the delamination of LRH-oleate. FE-SEM observation found that most of the exfoliated nanosheets have lateral sizes of ≥20 μm (Figure 4a). The uniform contrast under TEM (Figure 4b) of the individual nanosheets implies that the nanosheet is rather thin. Selected area electron diffraction (SAED) yielded well-arranged spot-like patterns, suggesting that the nanosheet under observation is well crystallized and is of single crystalline (inset in Figure 4b). The cell parameters calculated from the SAED pattern are a ~ 1.27 and b ~ 0.72 nm, in good agreement with those of the bulk LRH [21]. The nanosheet was estimated to be approximately 1.55 nm thick from the AFM height profile (Figure 4e), indicating that the nanosheet is primarily of unilamellar. At the same time, AFM observation indicated that the nanosheets are very flat and smooth (Figures 4c,d). Possibly due to surface chemical adsorption of oleate and toluene molecules, the unilamellar nanosheets are a little thicker than the crystallographic thickness of 0.93 nm [24]. Compared with those reported previously [22,23], the unilamellar nanosheets obtained in this work showed a significantly larger lateral size and a more unabridged shape, which is advantageous for the construction of highly oriented functional films.Figure 4

Bottom Line: The intercalation of oleate anions led to extremely expanded interlayer distances (up to approximately 5.2 nm) of the LRH crystals and accordingly disordered stacking of the ab planes along the c-axis and also weakened interlayer interactions, without significantly damaging the ab plane.Highly [111]-oriented and approximately 100-nm thick oxide films of (Y0.96Tb x Eu0.04-x ) 2O3 (0 ≤ x ≤ 0.04) have been obtained through spin-coating of the exfoliated colloidal nanosheets on quartz substrate, followed by annealing at 800°C.Upon UV excitation at 266 nm, the oxide transparent films exhibit bright luminescence, with the color-tunable emission from red to orange, yellow, and then green by increasing the Tb(3+) content from x = 0 to 0.04.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, No. 3-11, Wenhua Road, Shenyang, Liaoning 110819 China.

ABSTRACT
Efficient exfoliation of well-crystallized (Y0.96Tb x Eu0.04-x )2(OH)5NO3 · nH2O (0 ≤ x ≤ 0.04) layered rare-earth hydroxide (LRH) crystals into tens of micron-sized unilamellar nanosheets has been successfully achieved by inserting water insoluble oleate anions (C17H33COO(-)) into the interlayer of the LRH via hydrothermal anion exchange at 120°C, followed by delaminating in toluene. The intercalation of oleate anions led to extremely expanded interlayer distances (up to approximately 5.2 nm) of the LRH crystals and accordingly disordered stacking of the ab planes along the c-axis and also weakened interlayer interactions, without significantly damaging the ab plane. As a consequence, the thickness of the LRH crystals increased from approximately 1 to 10 μm, exhibiting a behavior similar to that observed from the smectite clay in water. Highly [111]-oriented and approximately 100-nm thick oxide films of (Y0.96Tb x Eu0.04-x ) 2O3 (0 ≤ x ≤ 0.04) have been obtained through spin-coating of the exfoliated colloidal nanosheets on quartz substrate, followed by annealing at 800°C. Upon UV excitation at 266 nm, the oxide transparent films exhibit bright luminescence, with the color-tunable emission from red to orange, yellow, and then green by increasing the Tb(3+) content from x = 0 to 0.04.

No MeSH data available.


Related in: MedlinePlus